1281999 has 4 divisors (see below), whose sum is σ = 1709336. Its totient is φ = 854664.

The previous prime is 1281983. The next prime is 1282007. The reversal of 1281999 is 9991821.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 1281999 - 2⁴ = 1281983 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1281979) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 213664 + ... + 213669.

It is an arithmetic number, because the mean of its divisors is an integer number (427334).

2^1281999 is an apocalyptic number.

1281999 is a deficient number, since it is larger than the sum of its proper divisors (427337).

1281999 is an equidigital number, since it uses as much as digits as its factorization.

1281999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 427336.

The product of its digits is 11664, while the sum is 39.

The square root of 1281999 is about 1132.2539467805. The cubic root of 1281999 is about 108.6331973573.

The spelling of 1281999 in words is "one million, two hundred eighty-one thousand, nine hundred ninety-nine".